In reply to SenzuBean:
Just a note on handheld 'thingys' - grippers are a great way to train crushing strength when you invest in good quality, heavy duty grippers (such as Captains Of Crush). However, firstly a decent gripper workout is something you should approach with the same seriousness as a hangboard workout (or any other type of training), not while sitting at your desk at work. You wouldn't stick a barbell with double your bodyweight in the corner of your office a knock out a deadlift every half hour in between sending emails. Secondly, crushing strength (that is, closing the hand tight into a fist) isn't something rock climbers really use, and therefore not something they would benefit from training extensively.
There's a reason heavy grippers aren't a popular form of grip training among climbers, despite being popular among those with an interest in general grip training. They simply aren't sport specific. They're quite satisfying to train with though!